I think the thing that pisses me off the absolute most is that Ebay is pitting the sellers against the buyers. I'm the type of person who wants to give people the benefit of the doubt.
I used to assume someone was telling the truth or had a legitimate reason for whatever problem we were dealing with... now (and I hate this but can't seem to stop) my first thought when a problem arises is "Great, another scammer (or non-payer, loser, etc...)".
Ebay has set us up to have to jump to the worst conclusions first just to protect ourselves. I used to immediately refund or cancel transactions when a customer told me there was a problem. Now I ask for proof, or use the "seller has not paid" UPI instead of the mutual disagreement.
Before I left Ebay I had 3 buyers in 1 month back out, then say no to the mutual agreement even after I explained exactly what it was and why I needed to do so. I hate having to give out strikes when someone needs/wants to back out of a sale, I don't believe is forcing buyers to complete the transaction if they run into a problem financially or figure out they just didn't want the set but, especially with the much higher fees, I can't afford to lose my FVFs on that many items simply because the buyers are being jerks.
It used to be a very small minimum of buyers who scammed or were jerks because it would show, as a negative, on their account. Now I've had people who decided to come screw with someone (and I happened to be the unlucky someone) because they had a crappy day.
Ebay has become a dumping ground for other people's frustrations and a scammer or thief's paradise and like others have said... the risk has simply become too great, especially for the small to mid sized seller.